Emulators allow software developers to test software that is targeted for particular devices without having the actual device at hand. For example, an emulator can be used to simulate how a particular software program designed for a personal digital assistant or phone device will look and operate without loading it on a physical device. Behind the scenes, emulators emulate the memory management unit of the processor of a respective device. This means that addresses inside the emulator must be translated to addresses on the host compiler. A particular software program typically runs slower using an emulator as opposed to running the program on the native device.